Freeze drying system and apparatus therefor



Sept. 17, 1968 M. 1.. BREWSTER FREEZE DRYING SYSTEM AND APPARATUS THEREFOR 4 Sheets-Sheet 1 Filed March 9, 1967 INVENTOR. MQRSHALL Z. BQEA/STEE BY flrroenjsv P 1968 A M, L. BREWSTER 3,401,466-

FREEZE DRYING SYSTEM AND APPARATUS THEREFOR Filed March 9, 1967 4 Sheets-Sheet 2 I N VEN TOR. M42SH01. 4 L 32501137762 FREEZE DRYING SYSTEM AND APPARATUS THEREFOR Sept. 17, 1968 M. L. BREWSTER 4 Sheets-Sheet 3 Filed March 9,

DEFROsT MEDIA has] ' DEFQosT MEDIA M42910 LBenJsTa? BY add... 7 2 fl-rrmalzx Sept. 17, 1968 M. 1.. BREWSTER 3,401,466

FREEZE DRYING SYSTEM AND APPARATUS THEREFOR Filed March 1967 4 Sheets-Sheet A MnzsHnLz 1;. Baa-M57152 INVENTOR.

' BY 4% hz 3 flTT'oQA/E Y United States Patent 3,401,466 FREEZE DRYING SYSTEM AND APPARATUS THEREFOR Marshall L. Brewster, Los Angeles, Calif. (7121 Canby Ave., Reseda, Calif. 91335) Filed Mar. 9, 1967, Ser. No. 621,806 Claims. (Cl. 34-92) ABSTRACT OF THE DISCLOSURE A freeze drying system employing an inert atmosphere dry room in direct receiving communication with a double-doored vacuum drying chamber whereby the dried product passes directly from the chamber into the dry room. The inert atmosphere supply system is also coupled to the vacuum drying chamber for breaking the vacuum and saturating the dried product with inert gas. A novel vacuum drying chamber apparatus with separately or jointly operable freeze-out condenser sections within the same structure but shielded against radiant heat transmission and provided with separately or jointly operable vacuum lines.

Background of the invention (1) Field of the inventi0n.The present invention relates to a freeze drying system involving inert packaging techniques and to methods and apparatus for handling, processing and packaging of foods, feeds, biologicals, pharmaceuticals and other materials bythe vacuum freeze drying process and, more particularly, to an improved overall method of practicing such process, to an improved method and apparatus therefor for final handling and packaging of the final dried product, and to an improved vacuum chamber with isolated internal vapor freeze-out condenser apparatus for facilitating the foregoing method as well as obtaining additional improved and advantageous features for such apparatus generally.

Freeze dried foods or materials are among the most sensitive types of processed materials. It is well known that the quality of finished dried product is affected by the original product, the processing and the storage and packaging techniques. Thus, variations in the process parameters and variables tend to cause exceedingly important influences on the final product such as deterioration of the product during storage, so that even the most careful and expensive techniques for packaging of the dried product cannot avoid the inherent problems created during the processing steps. Such variations may determine not only the storage life of the final product but even its very acceptability at all even prior to packaging. One of the most important factors in determining the acceptability of the product relates to the microbiological aspects and the relatively great susceptibility of freeze dried materials to oxidation which may cause both physi-' cally and chemically harmful and deleterious results as,

well as cause aesthetically undesirable appearance of the product.

(2) Description of the prior art.-The prevailing practice and procedure is to employ a single-ended vacuum drying chamber whereby the frozen wet material is placed within the chamber from one end and, when the drying cycle is completed, the dried material is removed from the same end into the environmental air which contains atmospheric oxygen and moisture. Since freeze dried foods and other materials have a relatively great internal surface area which readily absorbs atmospheric oxygen and moisture and permits the rapid diffusion of the oxygen and moisture throughout the dried material when exposed to air, a relatively great uptake of the environmental air occurs while the dried material is being transferred from the vacuum drying chamber to the final packaging facility. Since, for many reasons well known in the art as well as those discussed above, it is highly desirable and in some cases even essential that no moisture, oxygen or other ingredients of environmental air be permitted to remain in dehydrated products, especially freeze dried material, there have been many attempts to overcome this difiiculty. Suchattempts have included efforts to maintain the drying material within the vacuum drying chamber for extremely-long periods of time so as to completely remove all but a trace of moisture. However, in addition to being economically unfeasible, such efforts are largely wasted in that. the quantity of environmental air absorbed and dilfused through the material during transfer from the drying chamber to the packaging facility merely replaces that quantity of air and moisture which has been so slowly and meticulously removed during the final two or three hours of the extended drying cycle.

Other past attempts have included the use of various means at the packaging facility to remove the uptake air and moisture such as, for example, purging of the food or material by additional vacuum apparatus and by means of radiant or microwave heaters or the use of nitrogen gas by means of hose or chamber applicators at the instant before and while the product is packed or filled into its eventual containers. However, such methods are neither completely successful nor desirable in many instances because of the nature of the product and/or the inability of such means to accomplish the objective once the deleterious absorption and diffusion of the ambient atmosphere and all of its various ingredients has occurred.

Additional problems in the prior art relate to the types of vacuum drying apparatus employed in that they require complete shutdown of the apparatus in order to remove the accumulated ice from the condenser plates, if directly associated with the dryer, or else separate location of the condenser apparatus with the concomitant problems.

Summary of the invention Accordingly, it is one of the objects of the present invention to provide a method and apparatus therefor for preventing the uptake by or return to the vacuum freeze dried product of the previously removed atmospheric oxygen and moisture by preventing the exposure of the freeze dried material to the ambient air with its atmospheric oxygen and moisture content, such prevention being continued through the final packaging and, therefore, effectively until the material is ready for use or-consumption.

Additional and related objects of the present invention include the prevention of the uptake or reutrn of atmospheric oxygen and moisture as well as the reduction of the microbiological hazard and of oxidation to the lowest attainable extent, eliminating the unloading of the dried material from the same atmospheric (wet) side of the drying chamber means into which it was loaded, transferring or passing the dried material directly from the drying chamber into an inert atmosphere dry room or enclosure, employing the vacuum drying chamber as an environment barrier and dry nitrogen impregnator between the ambient atmosphere and the dried material before, as and after the dried material is removed from the drying chamber, providing containers with a dry, purified nitrogen atmosphere content at the time of packing automatically rather than by purging before filling, eliminating atmospheric oxygen head space in the final containers and generally providing a faster, more efficient, and ultimately less expensive overall system for vacuum freeze drying of materials and providing such materials 3 with improved characteristics both initially and over indefinitely extended shelf life.

Further objects relate to the provision of a novel combined vacuum dryer and condenser apparatus for maintaining the drying operation while achieving removal of accumulated ice or frozen condensate from the condenser plates for improved and more rapid vacuum drying, for obtaining loading of the apparatus with the frozen product from a wet or ambient atmosphere side and removal of the dried product into an inert environment, and for providing a functional as well as structural barrier between the ambient atmosphere and an inert atmosphere during and as an integral part of an overall freeze drying system.

In accordance with the present invention, there is provided a method where-by the vacuum freeze dried material is saturated with purified dry nitrogen and then passed or transferred directly from a vacuum drying chamber means into a dry non-oxidizing nitrogen environment within which final handling, processing and packaging of the dried product is performed. Apparatus is provided for movement and transfer of the various devices and apparatus used and useful in the overall system without unduly interfering with the maintenance of such environment and permitting both the continuous and intermittent presence of operating personnel for performing the various operational and control procedures normally deemed desirable or essential in the fin-al operations of the system.

The combined vacuum dryer and condenser apparatus of the present invention includes a single structure defining a central longitudinal chamber with doors at both ends and a pair of longitudinal chambers at each side thereof, the side chambers accommodating respective sets of condenser plates. Each of the side chambers is coupled through selectively operable valves to an external vacuum pump and is provided with large-passage valve means communicating with the central chamber whereby a vacuum can be created and maintained in all three chambers initially and just the central chamber and either one of the side chambers during subsequent defrosting of the other side chamber. The water vapor evolving from the frozen product during the drying cycle similarly passes through the large-passage valve means for condensation on the condenser plates, while the latter are otherwise physically separated from the central chamber whereby isolation is maintained between the cold condenser plates and the means for generating the heat for vaporization.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings.

Brief description of the drawings FIGURE 1 is a plan view, primarily diagrammatic and partly broken away and sectioned, showing the apparatus of the present invention disposed in a preferred plant layout embodiment for the practicing of the present invention;

FIGURE 2 is an elevation view, largely diagrammatic and partly sectioned, as seen from the right side of FIG- URE 1;

FIGURE 3 is an elevation view of a shelf car and product tray apparatus in accordance with the present invention;

FIGURE 4 is an enlarged fragmentary sectional elevation view as seen along line 44 in FIGURE 3;

FIGURE 5 is a fragmentary enlarged elevation view, partly in section, of the air supply system for the human operators in the packaging room;

FIGURE 6 is a diagrammatic sectional elevation view of the vacuum drying chamber apparatus in accordance with the present invention;

FIGURE 7 is an enlarged elevation view, partly broken away and sectioned, of the vaccum drying chamber apparatus of FIGURE 6;

FIGURE 8 is an elevation view, partly broken away and sectioned, as seen from the right side of FIGURE 7; and

FIGURE 9 is an enlarged sectional view of a portion of a condensing coil plate as seen along line 99 in FIGURE 7.

Description of the preferred embodiment Referring to FIGURES l-S of the drawings, and particularly to FIGURE I initially, there is diagrammatically illustrated a plant layout for a vacuum freeze drying system in accordance with the present invention having. main walls 10 defining a main room 11 within which the apparatus is located and the invention is practiced. Within the main walls 10 are located a plurality of interior enclosures including a blast freezer 12 capable of attaining and maintaining a temperature of at least -40 F. for freezing the wet material, a vacuum drying chamber apparatus 14 of a preferably particular construction and configuration as described hereinafter, and an inert atmosphere room, the interior of which is indicated generally at 16 and which constitutes the dry material unloading area and final handling, treating and packaging room within which all final steps are performed so that the final product or material is never exposed to the hazards of moisture or oxygen once the material has been freeze dried and does not leave the final area 16 until it is protectively packaged and ready for storage, marketing or any other subsequent activities. Additional included enclosure comprise an entry or dressing room area 18, an airtrap passage 20, the latter communicating with the main room 11, the entry room 18 and the dry room 16 by means of respective doors 22, 24 and 26. Doors 22 and 26 constitute the sole means (other than the drying chamber 14 and any normally sealed emergency exits which may be provided) of entrance to and exit from the dry room 16 for both personnel, apparatus and packaged materials and thus, as will be readily appreciated, the doors 22 and 26 are in passageway alignment with each other for ready communication and mobility of empty tray carriers and finished product between the dry room 16 and the main room area 11.

Disposed with the main area 11 defined by the enclosure walls 10 are a plurality of tracks and rails communicating between the various areas and apparatus for assisting in the handling of the material and the movable equipment, such tracks and rails including a pair of parallel floor tracks 28 and 30 passing entirely through the drying chamber 14 parallel to the longitudinal axis thereof and having their opposite ends terminating within the inert atmosphere room 16 and adjacent the freezer 12, the tracks 28 and'30 being adapted to support a platen car 32 and having sufiicient length to accommodate the platen car 32 exteriorly of the drying chamber 14 beyond each of the end doors 34 and 36 at opposite ends of the drying chamber 14. As will be understood more clearly hereafter, in lieu of platen car 32, platens may be fixed within the drying chamber in such a manner as to allow the tray carriers to move into the dryer and interleave into the end and either side of the platens centilevered on a central supporting upright and horizontal beam, referred to in the art as the Christmas tree design. In this fashion, the fioor tracks 28 and 30 and the platen car 32 may be eliminated. The transportation tracks and rails furtherinclude a pair of parallel overhead tracks 38 and 40 of conventional I-beam construction, located transversely to the platen car tracks 28 and 30 within the main room 11 and adapted to transversely support a plurality of monorails 42 for movement along the tracks 38 and 40. A second pair of parallel overhead tracks 44- and 46 is'located within the dry room 16 parallel to the main room tracks 38 and 40 and are similarly provided with a plurality of the movable monorails 42. As illustrated, a network of fixed monorails 48A-48F'are arranged in a network within the main room 11, the freezer 12 and passageway 20 and are provided with suitable releasable interlocks for connection with the movable monorails 42 when the latter are arranged in alignment therewith. There is provided a plurality of tray carriers 52 adapted to be movably mounted as by wheels 54 on the monorails 42 and 48 whereby the tray carriers 52 can be rolled on such monorails or carried by the movable monorails 42 for transportation and utilization throughout the various areas within the enclosure 10.

The inert atmosphere for the dry room 16 is provided with a constant supply of fresh purified dry nitrogen, through at least one inlet port 56, from an adjacent reservoir of tanks containing nitrogen under high pressure, comprising a fully automatic system. The purified dry nitrogen atmosphere pressure within the dry room 16 is maintained slightly above constantly changing outside environmental atmosphere by means of a pressure modulator. Thus, any migration of atmosphere will be from the dry room 16 outwardly, such as the tumbling of nitrogen atmosphere outwardly through the entry and exit passageway 20. The environmental nitrogen atmosphere of dry room 16 is circulated and recirculated through typical air conditioning ducts constituting a completely closed system through wall floor outlet vent 58 and duct 60, through the vapor and particle filter 62, ultra-violet section 64 and cooling and/or heating section 66, returning to dry room 16 through ceiling duct 68 and inlet port 56. The air conditioner and purifier remove the food powder dust created during the unloading, milling, blending and pack-out of the product, and removal of other contaminants. The dry room 16 also serves as a sterile clean room. I

Although not shown therein for convenience and clarity of illustration and description, it will be appreciated that all of the equipment and apparatus for final handling, treatment and packaging of the final dry product after it is removed from the drying chamber 14 are all located within the inert atmosphere or dry room 16 whereby any possibility of exposure of the freeze dried material to oxygen or moisture is completely eliminated. Thus, the final product does not leave the packaging room 16 until it is disposed within suitable containers adapted to withstand and prevent the entry of moisture and oxygen until the package or container is ultimately opened by the consumer and ready for final use.

In order to provide for the comfort and safety of the personnel operating within the inert, nomlife-supporting nitrogen gas environment of the packaging room 16, the ceiling 70 of the room 16 is provided with an outside atmosphere supply system comprising a plurality of housings such as the one indicated at 72, each having an airsupply hose 74 coupled thereto and communicating through the ceiling 70 with a plurality of personnel supply hoses 76 via a subjacent housing 78 of preferably rotatable construction, each personnel air hose 76 being coupled to a helmet 80 adapted to be worn by the individual operator for supply of normal atmospheric air thereto. Preferably, the operator wears a total suit of airtight construction in communication with the helmet 80, and the air hoses 74 and 76 include exhaust hose means whereby the air is circulated throughout the helmet and suit and exhausted exteriorly of the dry room 16 in order to avoid the possibility of contamination of the inert atmosphere within the dry room 16 by moisture or other vapors emanating from the operator, The air hoses 76 are provided with a quick-detach coupling attachment 82 for coupling the hose 76 to the helmet 80 whereby the operator can dress within the entry room 18 and provide himself with a suitable auxiliary air supply until sequential entry through doors 24 and 26 into the dry room and coupling of his air hose 76 to his face mask or helmet obviously, the reverse procedure is employed when the operator leaves the dry room.

Referring to FIGURES 6-9, there is seen a preferred embodiment of a drying chamber 14 in accordance with the present invention having particular utility in the previously described system. The end doors 34 and 36 at opposite ends of the chamber 14 are individually releasably secured in closure relationship to the chamber by a plurality of conventional lock means so that the wet side door 34 may be opened to permit entry of the platen car 32 and its interleaved trays 154 with their frozen wet product into the drying chamber, the dry side door 36 being similarly operable for removal of the foregoing apparatus with the dried product after completion of the drying cycle. The drying. chamber apparatus 14 comprises a semi-cylindrical tube portion 104 located below an effectively median horizontal longitudinal plane and having a plurality of circular ribs 106 constituting a continuum about the chamber for assuring the physical strength thereof. A pair of parallel vertical longitudinal spaced plates 108 define a central longitudinal region or chamber through the apparatus 14 and are secured as by welding in airtight engagement at their lower extremities with the tube portion 104 and are adapted to be sealed in airtight engagement at their upper extremities by a corresponding pair of pivotally mounted plate valves 110 so that the so-defined central chamber can be sealed from either or both of the lateral or side regions or chamber hereinafter described.

Such side chambers being substantially identical, only one thereof and its contents will be described. A plurality of longitudinally abutting vertical plates 112 are secured at their lower extremities to the tube portion 104 and at their upper extremities to a continuous plate member 114 as by removable bolts 116'. Thus, a side chamber is defined by the vertical inner plate 108, the vertical outer plates 112, the portion of the tube member 104 therebetween, the valve plate 110 (when in its closed position as indicated by the phantom lines), and a portion of the top member 114, such side chamber region being generally referenced at 116. Thus, the side chamber 116 is adapted to be completely separated and sealed from the central chamber of the apparatus 14 defined by the vertical plates 108 and, with the construction illustrated, is particularly adapted for encompassing a plurality of condenser plates or coils 118. The condenser plates 118 are gang connected in modular sections between adjacent ribs 106 for ready removal from the region 116 as by removal of its corresponding vertical outer plate 112 whereby repair or replacement of individual sections of condenser plates 118 can be accomplished without removal of other portions of the apparatus, thereby assuring minimum periods of disuse of the dryer apparatus 14 when repairs or replacements are necessitated. The condenser plates 118 are provided with inlet and outlet ports 122 which are gang connected as by manifolds 124 to a refrigeration system 126.

A vacuum system for evacuating all chambers of the apparatus 14 comprises a pump and appropriate valves 132 connected to lateral conduits 134 which are disposed in exit port relationship to the side chambers 116 at the lower extremities thereof whereby the air flow during evacuation, and the evolved vapor fiow from the product during sublimation, is from the central chamber, through the upper valved passageway 136, and between and over the condenser plates 118 in the side chambers 116.

For defrosting of the condenser plates and coils, a conduit 138 is ported into the side chamber 116 at the upper extremity thereof and suitable defrost media, such as high pressure steam, is admitted via a valve 140 whereby the condensed vapor from the product which has become frozen on the condenser plates 118 into ice form is melted and washed down through a drain 142 provided with an appropriate drain valve 144.

It should be particularly noted that either of the side chambers 116 may be closed off from the central chamber during the vacuum drying operation by merely closing its corresponding vacuum valve 132 as by manual means (not shown). Alternatively, however, the vacuum pump valve 132 of either side chamber 116 may be closed and a relatively massive amount of preferably dry purified nitrogen may be introduced through a port 146 so that a high differential pressure rapidly forms between the central chamber and such un-evacuated side chamber 116 whereby the plate valve 110 is caused to pivotally swing upwardly into sealed engagement with its corresponding vertical plate member 108 for closing of the passageway 136, thereby permitting defrosting of the condenser plates 118 within such side chamber 116 by means of the foregoing defrosting procedures without necessitating breaking the vacuum within the central chamber or otherwise interfering with the continuance of the vacuum drying cycle, as the opposite side chamber 116 and its corresponding plates continue to function in a normal condensing and vacuum-maintaining manner.

This procedure is alternated throughout the length of the drying cycle, thus eliminating down time for defrosting. The chamber 14 can be reloaded immediately following unloading into the dry side 16 as aforementioned. Furthermore, efficiency of the freeze-out condenser plates is improved because thick accumulation of ice is minimized by the automatic alternating defrosting. Power (energy) cost is reduced, and water-vapor freeze-out (condensate removal) capability is increased beyond normal surface area capacity.

It should be noted that, in accordance with the present invention, the water vapor freeze-out condenser plates 118, which are normally maintained at about 40 F. or lower, are isolated from the platen car 32 and its heating platens or shelves 162 which are normally heated to 350 F. approximately. Thus, what may be referred to as the battle of the B.t.u.s between the radiant heat from the heate d platens or other sublimation-causing means in the central drying chamber and the essentially cold condenser plates 118 in the side condensing chambers 116 is effectively eliminated by the vertical bulkheads or plates 108 which isolate such chambers. Preferably, the central chamber side of each of the plates 108 is painted with brilliant while epoxy-resin paint to reflect the heat back within the central chamber, further increasing the radiant heat emissivity throughout the product suspended between the heated shelves.

The previously described construction of the combined vacuum dryer and condenser 14 with separately sealable side condenser chambers 116 permits the accomplishment of another important objective of the present invention in that, during the terminal portion of the drying cycle as may be precalculated or indicated by normal instrumentation, the central chamber can be completely sealed off and pressure isolated from the side chambers 116 by closing both of the valves 110, thus preventing removal to the condensing chambers 116 of any vapor that may be emanating from the frozen product, and checking to see if there is any vapor pressure rise within the central chamber as by a pressure sensor 148 (indicated diagrammatically in FIGURE 6) within the central chamber. Such a rise indicates that complete drying has not occurred yet and sublimation is still taking place, whereupon the valves 110 (or either of them) are reopened for continuation of the drying cycle. Such a pressure check is positive confirmation of actual drying conditions and is impossible in structures where the condenser plates are exposed and cannot be isolated.

Although the operation of the illustrated overall system should now be clear, a complete example of an operative cycle will be described with reference to the drawings to enhance a further understanding of the present invention.

The initial product is brought into the main room 11, as via doorway 150, and initial product preparation is performed at and along counter 152. The prepared wet product is loaded at the end of the counter 152 onto product trays 154- which are placed on cantilevered runners or shelves 156 of a product tray carrier 52 (see FIG- URES 3 and 4), the latter being suspended on monorail track portion 48A and transported therealong through entrance doorway 158 of the freezer 12 for disposition at either of portions 48B. A plurality of carriers 52 are so disposed. After quick-freezing of the wet product is accomplished, the carriers 52 are moved onto monorail portions 48C for freeze-holding and availability for removal from the freezer 12, also releasing portions 48B for receiving additional tray carriers with fresh wet product thereon. It may be noted here that once the product trays 154 have been placed on their respective tray carriers 52 at the initial loading point, they never leave the carriers 52 until they are unloaded within the dry room 16. Continuing the operational description, a plurality of tray carriers 52 and their frozen wet product loads are removed from the freezer 12 through exit doorway 160 and disposed on one or more movable monorails 42 for loading onto a platen car 32. The dryer door 34 is opened and the platen car 32, if the movable type, is rolled out on floor tracks 28 and 30 into position for receiving the shelves 156 and trays 154 in an interleaved manner from both sides thereof. Alternatively, as previously described, the heating platens 162 may be fixed within the dryer 14 or the platen car 32 may be \left within the dryer 14, in either of which events the tray carriers 52 are interleaved between the platens 162 through the dryer end made accessible by the open door 34.

Upon completion of the drying cycle, the drying chamber 14'becomes an integral and critical part of the inert atmosphere packaging technique involving the dry room 16. When the drying cycle is consummated, the vacuum within the freeze dry chamber 14 is broken with the introduction of purified dry nitrogen through parts 146 and a port 164 (FIGURE 7) supplied from the nitrogen supply system. The vast internal surface area of the honeycomb-like structure of the freeze-dried material is completely permeated and saturated throughout with the inert nitrogen, replacing the evacuated moisture and oxygen. When the nitrogen atmosphere pressure within the drying chamber 14 equals the atmospheric pressure of the inert nitrogen environment of the dry room 16, door 36 on the dry side of the chamber is opened. Thus, the sensitive and moisture loving freeze-dried material is retained and contained in a dry purified nitrogen environment, and is truly purged to the lowest possible degree of all oxidizing factors. Furthermore, the unloading, milling, blending, granulating, tableting, and packaging of the product within the dry room 16 inert environment, insures indefinite shelf life until such time as the protective packaging is broken for ultimate use. Chamber door 36 is closed, performing the function of an air lock, door 34 is opened on the wet side, the dryer is reloaded and the drying cycle is resumed.

The emptied product tray-s 154 and their carriers 52 are handled within the dry room 16, utilizing the monorails 42 as needed, and returned to the main room 11 through airlock passageway 20 via track portion 48D and main room monorails 42 for disposition on track portion 48B and its turntable portion 166 for eventual return to the initial loading track portion 48A. The packaged product is similarly removed from the dry room 16 through passageway 20.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a freeze drying system comprising a main room for preparation of a wet product, a freezer communicating with the main room for receiving the wet product therefrom and providing a frozen wet product thereto, and

a vacuum drying chamber means for receiving the frozen wet product and providing a dried product therefrom, the improvement comprising, in combination:

a dry room adjoining said main room and said vacuum drying chamber means; and

a pair of aligned doors at opposite ends of said vacuum drying chamber means, one of said doors communicating with said main room for receiving the frozen Wet product, the other of said doors communicating with said dry room for permitting direct removal of the dried product from said chamber means to said dry room for handling and packaging thereof.

2. The improvement as defined in claim 1 including nitrogen supply means for selectively supplying dry purified nitrogen to said vacuum drying chamber means for both breaking the vacuum therein and saturating the dried product with nitrogen to prevent entry of undesired matter into the dried product.

3. The improvement as defined in claim 1 including nitrogen supply means for continuously supplying dry purified nitrogen to and circulating it through said dry room to provide an inert atmosphere environment for the said handling and packaging of the dried product.

4. The improvement as defined in claim 3 wherein said nilrogen supply means selectively supplies dry purified nitrogen to said vacuum drying chamber means for both breaking the vacuum therein and saturating the dried product with nitrogen to prevent entry of undesired matter into the dried product.

5. The improvement as defined in claim 4 including ambient atmosphere supply and exhaust means coupled to said dry room for the convenience and protection of human personnel within said dry room.

'6. The improvement as defined in claim 4 including track and rail means in transportation communication between said main room, freezer, vacuum chamber means, and dry room for selected transport of said product therebetween.

7. In a freeze drying system, vacuum drying chamber apparatus comprising:

enclosure means;

a pair of laterally spaced longitudinally parallel plate members defining a central longitudinal chamber and a parallel pair of longitudinal side chambers on opposite sides of said central longitudinal chamber within said enclosure means in airtight relationship to each other;

door means located at at least one end of said central chamber for selectively permitting access thereto;

a pair of large-passage valve means, each communicating between said central chamber and a respective one of said side chambers for selectively permitting and preventing communication therebetween;

condenser means disposed in respective ones of said side chambers; and

means for selectively and selectably creating and breaking a vacuum in each of said side chambers and said central chamber.

8. The apparatus as defined in claim 7 including nitrogen supply means for selectively supplying dr-y purified nitrogen to said central chamber.

9. The apparatus as defined in claim 8 wherein said door means comprises two doors located at opposite ends of said central chamber for selectively permitting insertion of a frozen wet product through one such end and removal of a dried product from the other such end.

10. In a freeze drying system, the apparatus as defined in claim 9 and, in combination, the improvement comprising:

a dry room communicating with said central chamber via such removal end only; and

said nitrogen supply means continuously supplying dry purified nitrogen to and circulating it through said dry room to provide an inert atmosphere for final handling and packaging of the dried product.

References Cited UNITED STATES PATENTS 3,132,930 5/1964 Abbott 3492 3,242,575 3/1966 Manaresi 34-92 3,247,600 4/1966 Togashi 3492 3,255,534 6/ 1966 Kan 34-92 3,271,873 9/1966 Harper 3492 3,299,525 l/l967 Thuse 3492 WILLIAM J. WYE, Primary Examiner. 

